In 729 litres solution of acid and water, the ratio of acid and water is 7 : 2. How many litres of water must be added to it to get the solution in which the ratio of acid and water is 5 : 3?
Answer & explanation
Correct answer: option 2
Acid : Water = 7 : 2
⇒ (7 + 2)units = 729
⇒ 9 units = 729
⇒ 1 unit = 81L
⇒ Acid = 7 x 81 = 567 L
⇒ Water = 2 x 81 = 162 L
Let quantity of added water be a,
⇒ \(\frac{567}{162 + a}\) = \(\frac{5}{3}\)
⇒ 3 x 567 = 5 x 162 + 5x
⇒ 1701 = 810 + 5x
⇒ 5x = 1701 - 810
⇒ x = 178.2 L
Therefore, 178.2 L of water must be added to make the ratio of acid and water 5 : 3.